Control valves are commonly used in process control systems. In general, a control valve may be used to manipulate a flowing fluid to regulate a process variable to a desired set point, to convey or deliver a fluid from a source to a destination, etc. A sliding stem control valve assembly typically includes a valve plug, a valve stem, and an actuator to provide the motive power via the valve stem to operate the valve (e.g., to position the plug or flow control member within the valve).
The valve trim includes a valve stem connection that couples or fastens the valve stem to the valve plug. In typical sliding stem valves, a threaded end of the valve stem is threaded directly into a central aperture of the valve plug. In an alternative sliding stem valve, a threaded end of the valve stem passes through a central aperture of the valve plug, and one or more mechanical fastening elements (e.g., washers, nuts, bolts, etc.) are used to clamp or otherwise fix the valve plug to the valve stem.
In operation, control valves may be subjected to high temperatures. At such high temperatures, the valve stem connection may become overloaded and/or loosen the valve stem from the valve plug, which may cause a valve stem connection failure.